/*
 * Copyright (c) 2006, 2012, Oracle and/or its affiliates. All rights reserved.
 * ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
 *
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 */

package java.io;

/**
 * Context during upcalls from object stream to class-defined
 * readObject/writeObject methods.
 * Holds object currently being deserialized and descriptor for current class.
 *
 * This context keeps track of the thread it was constructed on, and allows
 * only a single call of defaultReadObject, readFields, defaultWriteObject
 * or writeFields which must be invoked on the same thread before the class's
 * readObject/writeObject method has returned.
 * If not set to the current thread, the getObj method throws NotActiveException.
 */
final class SerialCallbackContext {

  private final Object obj;
  private final ObjectStreamClass desc;
  /**
   * Thread this context is in use by.
   * As this only works in one thread, we do not need to worry about thread-safety.
   */
  private Thread thread;

  public SerialCallbackContext(Object obj, ObjectStreamClass desc) {
    this.obj = obj;
    this.desc = desc;
    this.thread = Thread.currentThread();
  }

  public Object getObj() throws NotActiveException {
    checkAndSetUsed();
    return obj;
  }

  public ObjectStreamClass getDesc() {
    return desc;
  }

  public void check() throws NotActiveException {
    if (thread != null && thread != Thread.currentThread()) {
      throw new NotActiveException(
          "expected thread: " + thread + ", but got: " + Thread.currentThread());
    }
  }

  private void checkAndSetUsed() throws NotActiveException {
    if (thread != Thread.currentThread()) {
      throw new NotActiveException(
          "not in readObject invocation or fields already read");
    }
    thread = null;
  }

  public void setUsed() {
    thread = null;
  }
}
